1. Field of the Invention
The present invention relates to a method of forming a metal in a concave portion of a substrate, to a method of manufacturing a magnetic head that uses the method thereof, and to the magnetic head.
2. Description of the Related Art
A micro device such as a thin film magnetic head is manufactured by depositing a variety of films on a substrate by a sputtering, a plating method, or the like. JP Laid-Open Patent Application No. 05-290325 discloses a thin film magnetic head and a method of manufacturing thereof. The thin film magnetic head has a surface (air bearing surface) opposing a recording medium and generates a writing magnetic field from the air bearing surface.
The thin film magnetic head has a main pole part and an auxiliary pole part facing the air bearing surface. A coil layer is wound in the vicinity of the main pole part at a position separated from the air bearing surface that opposes the recording medium. A magnetic flux generated by the coil layer is guided inward of the main pole part and extends from the air bearing surface to the recording medium. The auxiliary pole part is a magnetic layer that magnetically couples with the main pole part at a position separated from the air bearing surface. The auxiliary pole part is separated from the main pole part as sandwiching an insulating layer on the air bearing surface. The auxiliary pole part refluxes the magnetic flux discharged from the main pole part via the recording medium.
When manufacturing the thin film magnetic head described above, or other micro devices, a step to form a metal in a concave portion on a substrate may be performed. An example of a method of forming a metal in a concave portion of a substrate by the plating method will be described with reference to FIG. 1A through FIG. 1D. In addition, FIG. 1A through FIG. 1D are drawings prepared by the applicants of the present application to describe a problem of the present invention.
FIG. 1A illustrates a substrate 300 where a concave portion 310 is formed on a surface. Normally, in order to form a metal only in the concave portion 310 on the substrate 300, as shown in FIG. 1B, a resist 301 of a predetermined pattern is formed on the substrate 300 using a photolithography method. Here, the resist 301 has an aperture in the position of the concave portion 310 of the substrate 300.
Next, a metal 302 is formed in the concave portion 310 of the substrate through the aperture of the resist 301, and then the resist 301 is removed (see FIG. 1C). The metal 302 can be formed by a plating method. The metal 302 gradually increases in thickness from the surface of the substrate 300 as the deposition time of plating proceeds. Accordingly, when attempting to form the metal 302 with a sufficient thickness in the center of the concave portion 310, the metal 302 highly builds up near the side surface of the resist 301. As a result, a large height difference 311 occurs at the edge part of the formed metal 302.
Particularly, when the concave portion 310 is deep, for example, having a depth of 3 μm or more, it is necessary to deposit the metal 302 with a thickness that is equal to or greater than the depth of the concave portion in order to form the metal 302 with a sufficient thickness even in the center of the concave portion 310. Therefore, the large height difference 311 is formed at the edge part of the formed metal 302.
As illustrated in FIG. 1D, when an insulating layer 303 is formed, for example, by sputtering in the periphery of such height difference 311, problems such as a crack 305, void 306, heterogenous phase 307, or the like, may occur in the insulating layer 303. The heterogenous phase 307 is a boundary between the insulating layer 303 grown from the surface of the substrate 300 and the insulating layer 303 grown from the height difference 311 of the metal, and an intensity of the insulating layer 303 weakens at the boundary. Therefore, the height difference 311 of the metal 302 is preferably as small as possible.
When the metal 302 is planarized, for example, by a chemical mechanical polish (CMP) before forming the insulating layer 303, this can suppress the occurrence of a crack, void, heterogenous phase, or the like in the insulating layer 303. However, there is a risk of damaging the surface of the metal 302 or structural objects formed in the substrate 300 by the CMP. Particularly, since micro devices such as the thin film magnetic head have minute structural objects formed in the substrate, it is preferred to reduce the damage caused by the CMP.
Therefore, a method is desired of forming a metal with the flat surface to the extent possible and with a low height difference in the concave portion of the substrate without conducting the CMP. Such method can be preferably utilized to manufacture, particularly, a micro device such as the thin film magnetic head.